With the ever increasing use of high frequency radio communications there is a need for low cost, high performance antennas. Generally, high frequency antennas are constructed in the familiar dish shape to focus the received radio frequency ("RF") energy by reflection onto an electronic receiver which then passes the radio signal to other electronic components to extract the data contained in the signal. In order to maximize the amount of RF energy reflected by the antenna, the electromagnetically reflecting surface of the antenna is provided with a metallic material, such as aluminum or nickel.
Modem low-cost, high-frequency antennas, such as those used in satellite dishes, are typically constructed as shown in FIG. 1. FIG. 1 depicts a high frequency antenna 100 in cross-section. The antenna 100 includes a core 102 which forms the parabolic dish shape used to receive and reflect the high frequency RF signals. As used herein the term "core" refers to the structural depending on the manufacturing technology used, the core 102 is normally either attached to, or formed integrally with, other structural portions of the antenna, such as mounting structures 104 which are used to attach the antenna to desired positioning equipment that establishes the core's physical location and orientation.
While numerous variations are possible, conventional low cost cores are normally constructed from a molded plastic material which is provided with a signal receiving surface, in this case parabolic surface 106, designed to reflect selected frequencies of electromagnetic radiation from the parabolic surface 106 to an electronic receiver 110. The receiver 110 then passes the received signal to other electronic components, such as amplifies, demodulators, etc., which process the signal into a usable form.
Since plastic is not itself electrically conductive, its electromagnetically reflective properties are poor. Therefore, the parabolic surface of the core must be made conductive by either molding a conductive material into the parabolic surface, or painting the parabolic surface with a conductive material. Neither of these techniques for manufacturing antennas are completely satisfactory.
The process of molding in a conductive material requires the use of a compression molding process. In compression molding, a two piece mold is normally used, and each piece of the mold corresponds to one-half of the antenna core 102. Therefore, when the molds are assembled, they create a cavity that is the same size and shape of the desired antenna core. In operation, the conductive material to be used as the reflective surface, for instance, a wire mesh, is placed in the mold half that forms the reflecting surface of the antenna core. An amount of plastic molding material is then placed into the other half of the mold and the mold halves are compressed together, forcing the plastic material into the desired core shape. After the plastic cures, the molds are separated and the plastic antenna core is removed. It will be clear that the wire mesh is permanently formed into the reflecting surface of the antenna core during the process.
However, the compression molding process for forming antenna cores suffers from several drawbacks. First, the process is only suitable with certain types of plastic materials referred to sheet molding compounds ("SMCs"). These compounds are relatively low in viscosity and precise weights of the SMC material must be provided for each mold. Generally, pieces of the SMC material are hand cut to match a given mold. This is a time consuming process which adds to the cost of the completed antenna core. Moreover, even after the core is fabricated using the compression molding process, the reflecting surface must still be painted in order to protect the reflecting material from environmental pollutants, such as moisture, airborne chemicals, and the like. The paints commonly used in the art often involve the release of volatile organic compounds ("VOCs") which are environmentally undesirable.